1. Field of the Invention
The present invention relates generally to rotary valves, and more particularly to an energy attenuating ball valve which includes an impedance assembly mounted within and movable with the closure element or “ball” of the ball valve.
2. Discussion of Background
There is currently known in the prior art linear valve assemblies which are outfitted to include a noise attenuation or impedance assembly. Such valves are often referred to in the relevant industry as “drag valves”. Linear valves as currently known in the prior art typically include an annular impedance assembly which includes a plurality of annular disks which each define a plurality of radially extending, tortuous flow passages and are secured to each other in a stacked arrangement. Disposed within the interior of the impedance assembly is a piston which is cooperatively engaged to an actuator operative to facilitate the reciprocal movement of the piston within the impedance assembly. When the piston is in a lowermost position, none of the passages of the impedance assembly are exposed to an incoming flow. As the piston is moved upwardly toward an open position, flow passes through the passages of the impedance assembly to provide an exit flow through the linear valve. The amount of flow through the impedance assembly is varied by the position of the piston, which in turn varies the area or proportion of the impedance assembly exposed to the incoming flow within the interior thereof.
Though the above-described linear valve arrangement provides significant noise reduction capabilities, in certain applications it is often desirable to employ the use of a rotary valve utilizing a rotary closure element as an alternative to a linear valve. Since currently known linear impedance valves are typically considered to provide superior noise reduction capabilities as compared to rotary valves, the present invention addresses this disparity by providing a rotary valve arrangement which retains the benefits of the impedance assembly associated with linear valves, while still employing the use of a rotary closure element. As will be discussed in more detail below, in the present invention, the impedance assembly is carried by the rotary closure element of the rotary or ball valve which may be adapted for use in large, high capacity applications for which an equivalent linear valve would be excessively expensive (attributable to manufacturing obstacles) and potentially susceptible to instability problems. These, and other advantages of the present invention, will be discussed in more detail below.